Angular UI pages when used as a variable (in UI page type variable) on service catalog items fails to render after upgrade to London.
This is caused because of the fix to PRB1240229. The changes skip the element from the angular compilation process if the element type is '.formatter.com_glideapp_servicecatalog_veditor' or '.formatter.com_glideapp_questionset_default_question_editor'.
To fix this, import the attached UI macro to the instance in question.
Note : It is better to move away from using the UI pages as variables as it is no more supported in the newer alternatives such as service portal.